1. Field of the Invention
The present invention relates to a thermal printer with a jam detection device which detects a jam of a recording material in a transport path through the thermal printer.
2. Background Arts
There are many types of color thermal printers, which are mainly classified into thermal transfer type such as ink transfer type and wax transfer type, and direct printing type using a thermosensitive recording material. A color thermosensitive recording material includes at least cyan, magenta and yellow recording layers which have different thermal sensitivities and develop respective colors in different heat energy ranges.
There is a single-pass multi-head type color thermal printer which has a plurality of, e.g. three thermal heads for the three colors, and in which a recording material, e.g. the color thermosensitive material, is passed through the thermal heads a single time to sequentially record three color frames of a full-color image, for example, as disclosed in JPA 5-201043 and JPB 6-96338. Platen rollers are disposed in opposition to the thermal heads to press the recording material onto the thermal heads while a designated recording area of the recording material passes through them.
The single-pass multi-head type has an advantage in that it takes a shorter time to print a full-color image, compared with a single-head three-pass type color thermal printer in which a sheet of color recording material is passed through a single thermal head three times to record a full-color image. However, as the transport path is elongated with the plural number of thermal heads, it is necessary to provide a plurality of pairs of rollers for transporting the recording material through the path. Because the transporting speeds of the roller pairs can change from one another, the recording material can get loose or tensed between the roller pairs. If the recording material is too loose, it jams between the roller pair. The greater the number of the roller pairs, the more the recording material is apt to jam.